Solve that and you will be one step towards the treasure. Honestly everybody believes something different. Do a search on the various websites related to this treasure and you will find some people believe it might be a sink, a tub, a general place like Yellowstone, where the boiling river turns colder, various hot springs, various geysers, the firehole river, and on and on.... There are lots of even more bizarre theories out there if you want to keep looking.

Most of the discussion takes place in the "General" portion of the site. Use the search tool and you will be instantly buried with threads discussing this.